In the state of the art, measuring devices are known, in which a so-called oscillatory fork, as a mechanically oscillatable unit, is excited to execute oscillations. Since the oscillations, i.e. their characterizing variables, such as frequency, amplitude and phase, depend on whether there is contact with a medium, and then on its properties, such as density or viscosity, such variables can be deduced from the characterizing variables of the oscillations. Thus, such a measuring device makes possible, for instance, monitoring fill level or measuring density of the medium.
It has been found that there are ranges of phase differences between the exciting and received signals, in which the behavior of the oscillatory system can be influenced in certain respects. Thus, for instance, detection of foam is enabled or suppressed. Additionally, dependence of the oscillations on changes of viscosity can be eliminated (see DE 100 57 974 A1). In order to achieve these effects, it is, however, necessary, that the desired phase values be achieved as exactly as possible.